1. Field of the Invention
The present invention relates to an optical plate for use in, for example, a backlight module, the backlight module typically employed in a liquid crystal display (LCD).
2. Discussion of the Related Art
A weight and/or a thickness of LCD panels makes them suitable for use in a wide variety of electronic devices such as personal digital assistants (PDAs), mobile phones, portable personal computers, and other electronic appliances. Liquid crystal is a substance that does not emit light. Instead, the liquid crystal relies on receiving light from a light source in order to display data images. In the case of a typical LCD panel, a backlight module powered by electricity supplies the needed light.
FIG. 11 is an exploded, side cross-sectional view of a typical direct type backlight module 10 employing a typical optical diffusion plate. The backlight module 10 includes a housing 11, a plurality of lamps 12 disposed above a base of the housing 11 for emitting light, and a light diffusion plate 13 and a prism sheet 14 stacked on a top of the housing 11 in that order. The housing 11 is configured for reflecting light towards the diffusion plate 13. The light diffusion plate 13 includes a plurality of dispersion particles. The dispersion particles are configured for scattering light, thereby enhancing a uniformity of light output from the light diffusion plate 13. A top of the prism sheet 14 includes a plurality of V-shaped structures. The V-shaped structures are configured for collimating received light to a certain extent.
In use, light from the lamps 12 enters the prism sheet 14 after being scattered in the light diffusion plate 13. The light is refracted in the prism sheet 14 and are concentrated by the V-shaped structures so as to increase a brightness of light illumination, and finally propagate into an LCD panel (not shown) disposed above the prism sheet 14. The brightness may be improved by the V-shaped structures, but the viewing angle may be narrowed. In addition, even though the light diffusion plate 13 and the prism sheet 14 abut each other, a plurality of air pockets still exists at the boundary between them. When the backlight module 10 is in use, light passes through the air pockets, and some of the light undergoes total reflection at one or another of the interfaces at the air pockets. As a result, the light energy utilization ratio of the backlight module 10 is reduced.
Therefore, a new optical means is desired in order to overcome the above-described shortcomings.